The Measurement of Intelligence Part 5

OTHER CONCEPTIONS OF INTELLIGENCE. It is interesting to compare Binet's conception of intelligence with the definitions which have been offered by other psychologists. According to Ebbinghaus, for example, the essence of intelligence lies in comprehending together in a unitary, meaningful whole, impressions and a.s.sociations which are more or less independent, heterogeneous, or even partly contradictory. "Intellectual ability consists in the elaboration of a whole into its worth and meaning by means of many-sided combination, correction, and completion of numerous kindred a.s.sociations.... It is a _combination activity_."

Meumann offers a twofold definition. From the psychological point of view, intelligence is the power of independent and creative elaboration of new products out of the material given by memory and the senses. From the practical point of view, it involves the ability to avoid errors, to surmount difficulties, and to adjust to environment.

Stern defines intelligence as "the general capacity of an individual consciously to adjust his thinking to new requirements: it is general adaptability to new problems and conditions of life."

Spearman, Hart, and others of the English school define intelligence as a "common central factor" which partic.i.p.ates in all sorts of special mental activities. This factor is explained in terms of a psycho-physiological hypothesis of "cortex energy," "cerebral plasticity," etc.

The above definitions are only to a slight extent contradictory or inharmonious. They differ mainly in point of view or in the location of the emphasis. Each expresses a part of the truth, and none all of it. It will be evident that the conception of Binet is broad enough to include the most important elements in each of the other definitions quoted.

GUIDING PRINCIPLES IN CHOICE AND ARRANGEMENT OF TESTS. In choosing his tests Binet was guided by the conception of intelligence which we have set forth above. Tests were devised which would presumably bring into play the various mental processes thought to be concerned in intelligence, and then these tests were tried out on normal children of different ages. If the percentage of pa.s.ses for a given test increased but little or not at all in going from younger to older children this test was discarded. On the other hand, if the proportion of pa.s.ses increased rapidly with age, and if children of a given age, who on other grounds were known to be bright, pa.s.sed more frequently than children of the same age who were known to be dull, then the test was judged a satisfactory test of intelligence. As we have shown elsewhere,[13]

practically all of Binet's tests fulfill these requirements reasonably well, a fact which bears eloquent testimony to the keen psychological insight of their author.

[13] See p. 55.

In arranging the tests into a system Binet's guiding principle was to find an arrangement of the tests which would cause an average child of any given age to test "at age"; that is, the average 5-year-old must show a mental age of 5 years, the average 8-year-old a mental age of 8 years, etc. In order to secure this result Binet found that his data seemed to require the location of an individual test in that year where it was pa.s.sed by about two thirds to three fourths of unselected children.

It was in the a.s.sembling of the tests that the most serious faults of the scale had their origin. Further investigation has shown that a great many of the tests were misplaced as much as one year, and several of them two years. On the whole, the scale as Binet left it was decidedly too easy in the lower ranges, and too difficult in the upper. As a result, the average child of 5 years was caused to test at not far from 6 years, the average child of 12 years not far from 11. In the Stanford revision an effort has been made to correct this fault, along with certain other generally recognized imperfections.

SOME AVOWED LIMITATIONS OF THE BINET TESTS. The Binet tests have often been criticized for their unfitness to perform certain services which in reality they were never meant to render. This is unfair. We cannot make a just evaluation of the scale without bearing in mind its avowed limitations.

For example, the scale does not pretend to measure the entire mentality of the subject, but only _general intelligence_. There is no pretense of testing the emotions or the will beyond the extent to which these naturally display themselves in the tests of intelligence. The scale was not designed as a tool for the a.n.a.lysis of those emotional or volitional aberrations which are concerned in such mental disorders as hysteria, insanity, etc. These conditions do not present a progressive reduction of intelligence to the infantile level, and in most of them other factors besides intelligence play an important role. Moreover, even in the normal individual the fruitfulness of intelligence, the direction in which it shall be applied, and its methods of work are to a certain extent determined by the extraneous factors of emotion and volition.

It should, nevertheless, be pointed out that defects of intelligence, in a large majority of cases, also involve disturbances of the emotional and volitional functions. We do not expect to find perfectly normal emotions or will power of average strength coupled with marked intellectual deficiency, and as a matter of fact such a combination is rare indeed. In the course of an examination with the Binet tests, the experienced clinical psychologist is able to gain considerable insight into the subject's emotional and volitional equipment, even though the method was designed primarily for another purpose.

A second misunderstanding can be avoided by remembering that the Binet scale does not pretend to bring to light the idiosyncrasies of special talent, but only to measure the general level of intelligence. It cannot be used for the discovery of exceptional ability in drawing, painting, music, mathematics, oratory, salesmans.h.i.+p, etc., because no effort is made to explore the processes underlying these abilities. It can, therefore, never serve as a _detailed chart_ for the vocational guidance of children, telling us which will succeed in business, which in art, which in medicine, etc. It is not a new kind of phrenology. At the same time, as we have already pointed out, _it is capable of bounding roughly the vocational territory in which an individual's intelligence will probably permit success, nothing else preventing_.[14]

[14] See p. 17.

In the third place, it must not be supposed that the scale can be used as a complete pedagogical guide. Although intelligence tests furnish data of the greatest significance for pedagogical procedure, they do not suggest the appropriate educational methods in detail. These will have to be worked out in a practical way for the various grades of intelligence, and at great cost of labor and patience.

Finally, in arriving at an estimate of a subject's grade of intelligence and his susceptibility to training, it would be a mistake to ignore the data obtainable from other sources. No competent psychologist, however ardent a supporter of the Binet method he might be, would recommend such a policy. Those who accept the method as all-sufficient are as much in error as those who consider it as no more important than any one of a dozen other approaches. Standardized tests have already become and will remain by far the most reliable single method for grading intelligence, but the results they furnish will always need to be interpreted in the light of supplementary information regarding the subject's personal history, including medical record, accidents, play habits, industrial efficiency, social and moral traits, school success, home environment, etc. Without question, however, the improved Binet tests will contribute more than all other data combined to the end of enabling us to forecast a child's possibilities of future improvement, and this is the information which will aid most in the proper direction of his education.

CHAPTER IV

NATURE OF THE STANFORD REVISION AND EXTENSION

Although the Binet scale quickly demonstrated its value as an instrument for the cla.s.sification of mentally-r.e.t.a.r.ded and otherwise exceptional children, it had, nevertheless, several imperfections which greatly limited its usefulness. There was a dearth of tests at the higher mental levels, the procedure was so inadequately defined that needless disagreement came about in the interpretation of data, and so many of the tests were misplaced as to make the results of an examination more or less misleading, particularly in the case of very young subjects and those near the adult level. It was for the purpose of correcting these and certain other faults that the Stanford investigation was planned.[15]

[15] The writer wishes to acknowledge his very great indebtedness to Miss Grace Lyman, Dr. George Ordahl, Dr. Louise Ellison Ordahl, Miss Neva Galbreath, Mr. Wilford Talbert, Dr. J. Harold Williams, Mr. Herbert E. Knollin, and Miss Irene Cuneo for their cooperation in making the tests on which the Stanford revision is chiefly based. Without their loyal a.s.sistance the investigation could not have been carried through.

Grateful acknowledgment is also made to the many public school teachers and princ.i.p.als for their generous and invaluable cooperation in furnis.h.i.+ng subjects for the tests, and in supplying, sometimes at considerable cost of labor, the supplementary information which was called for regarding the pupils tested. Their contribution was made in the interest of educational science, and without expectation of personal benefits of any kind. Their professional spirit cannot be too highly commended.

SOURCES OF DATA. Our revision is the result of several years of work, and involved the examination of approximately 2300 subjects, including 1700 normal children, 200 defective and superior children, and more than 400 adults.

Tests of 400 of the 1700 normal children had been made by Childs and Terman in 1910-11, and of 300 children by Trost, Waddle, and Terman in 1911-12. For various reasons, however, the results of these tests did not furnish satisfactory data for a thoroughgoing revision of the scale.

Accordingly a new investigation was undertaken, somewhat more extensive than the others, and more carefully planned. Its main features may be described as follows:--

1. The first step was to a.s.semble as nearly as possible all the results which had been secured for each test of the scale by all the workers of all countries. The result was a large sheet of tabulated data for each individual test, including percentages pa.s.sing the test at various ages, conditions under which the results were secured, method of procedure, etc. After a comparative study of these data, and in the light of results we had ourselves secured, a provisional arrangement of the tests was prepared for try-out.

2. In addition to the tests of the original Binet scale, 40 additional tests were included for try-out. This, it was expected, would make possible the elimination of some of the least satisfactory tests, and at the same time permit the addition of enough new ones to give at least six tests, instead of five, for each age group.

3. A plan was then devised for securing subjects who should be as nearly as possible representative of the several ages. The method was to select a school in a community of average social status, a school attended by all or practically all the children in the district where it was located. In order to get clear pictures of age differences the tests were confined to children who were within two months of a birthday. To avoid accidental selection, _all_ the children within two months of a birthday were tested, in whatever grade enrolled. Tests of foreign-born children, however, were eliminated in the treatment of results. There remained tests of approximately 1000 children, of whom 905 were between 5 and 14 years of age.

4. The children's responses were, for the most part, recorded _verbatim_. This made it possible to re-score the records according to any desired standard, and thus to fit a test more perfectly to the age level a.s.signed it.

5. Much attention was given to securing uniformity of procedure. A half-year was devoted to training the examiners and another half-year to the supervision of the testing. In the further interests of uniformity all the records were scored by one person (the writer).

METHOD OF ARRIVING AT A REVISION. The revision of the scale below the 14-year level was based almost entirely on the tests of the above-mentioned 1,000 unselected children. The guiding principle was to secure an arrangement of the tests and a standard of scoring which would cause the median mental age of the unselected children of each age group to coincide with the median chronological age. That is, a correct scale must cause the _average_ child of 5 years to test exactly at 5, the _average_ child at 6 to test exactly at 6, etc. Or, to express the same fact in terms of intelligence quotient,[16] a correct scale must give a median intelligence quotient of unity, or 100 per cent, for unselected children of each age.

[16] The intelligence quotient (often designated as I Q) is the ratio of mental age to chronological age. (See pp. 65 _ff._ and 78 _ff._)

If the median mental age resulting at any point from the provisional arrangement of tests was too high or too low, it was only necessary to change the location of certain of the tests, or to change the standard of scoring, until an order of arrangement and a standard of pa.s.sing were found which would throw the median mental age where it belonged. We had already become convinced, for reasons too involved for presentation here, that no satisfactory revision of the Binet scale was possible on any theoretical considerations as to the percentage of pa.s.ses which an individual test ought to show in a given year in order to be considered standard for that year.

As was to be expected, the first draft of the revision did not prove satisfactory. The scale was still too hard at some points, and too easy at others. In fact, three successive revisions were necessary, involving three separate scorings of the data and as many tabulations of the mental ages, before the desired degree of accuracy was secured. As finally revised, the scale gives a median intelligence quotient closely approximating 100 for the unselected children of each age from 4 to 14.

Since our school children who were above 14 years and still in the grades were r.e.t.a.r.ded left-overs, it was necessary to base the revision above this level on the tests of adults. These included 30 business men and 150 "migrating" unemployed men tested by Mr. H. E. Knollin, 150 adolescent delinquents tested by Mr. J. Harold Williams, and 50 high-school students tested by the writer.

The extension of the scale in the upper range is such that ordinarily intelligent adults, little educated, test up to what is called the "average adult" level. Adults whose intelligence is known from other sources to be superior are found to test well up toward the "superior adult" level, and this holds whether the subjects in question are well educated or practically unschooled. The almost entirely unschooled business men, in fact, tested fully as well as high-school juniors and seniors.

Figure 1 shows the distribution of mental ages for 62 adults, including the 30 business men and the 32 high-school pupils who were over 16 years of age. It will be noted that the middle section of the graph represents the "mental ages" falling between 15 and 17. This is the range which we have designated as the "average adult" level. Those above 17 are called "superior adults," those between 13 and 15, "inferior adults." Subjects much over 15 years of age who test in the neighborhood of 12 years may ordinarily be considered border-line cases.

[Ill.u.s.tration: FIG. 1. DISTRIBUTION OF MENTAL AGES OF 62 NORMAL ADULTS]

The following method was employed for determining the validity of a test. The children of each age level were divided into three groups according to intelligence quotient, those testing below 90, those between 90 and 109, and those with an intelligence quotient of 110 or above. The percentages of pa.s.ses on each individual test at or near that age level were then ascertained separately for these three groups. If a test fails to show a decidedly higher proportion of pa.s.ses in the superior I Q group than in the inferior I Q group, it cannot be regarded as a satisfactory test of intelligence. On the other hand, a test which satisfies this criterion must be accepted as valid or the entire scale must be rejected. Henceforth it stands or falls with the scale as a whole.

When tried out by this method, some of the tests which have been most criticized showed a high degree of reliability; certain others which have been considered excellent proved to be so little correlated with intelligence that they had to be discarded.

After making a few necessary eliminations, 90 tests remained, or 36 more than the number included in the Binet 1911 scale. There are 6 at each age level from 3 to 10, 8 at 12, 6 at 14, 6 at "average adult," 6 at "superior adult," and 16 alternative tests. The alternative tests, which are distributed among the different groups, are intended to be used only as subst.i.tutes when one or more of the regular tests have been rendered, by coaching or otherwise, undesirable.[17]

[17] See p. 137 _ff._ for explanations regarding the calculation of mental age and the use of alternative tests.

Of the 36 new tests, 27 were added and standardized in the various Stanford investigations. Two tests were borrowed from the Healy-Fernald series, one from Kuhlmann, one was adapted from Bonser, and the remaining five were amplifications or adaptations of some of the earlier Binet tests.

Following is a complete list of the tests of the Stanford revision.

Those designated _al._ are alternative tests. The guide for giving and scoring the tests is presented at length in Part II of this volume.

_The Stanford revision and extension_

_Year III._ (_6 tests, 2 months each._) 1. Points to parts of body. (3 to 4.) Nose; eyes; mouth; hair.

2. Names familiar objects. (3 to 5.) Key, penny, closed knife, watch, pencil.

3. Pictures, enumeration or better. (At least 3 objects enumerated in one picture.) (a) Dutch Home; (b) River Scene; (c) Post-Office.

4. Gives s.e.x.

5. Gives last name.